Voice operated circuit



Dec. 19, 1933. H, J, msi-1ER 1,939,680

voIcE OPERATED CIRCUIT Filed Dec. l, 1931 ATTORNEY Patented Dec. 19,

TES

[PATEN I' VOICE OPERATED CIRCUITV `Harold` J. Fisher, Port Washington,N. Y., asfsignor to Bell Telephone Laboratories, Incor- K Y An object ofthe invention is to enable speech currents to-exercis immediate andpositive control over the circuit which they-are intended to controlwhile at th`e-sametime preventing'false operation of that circuit bynoise currentsfwhich .10 may be present.

vVoice operated circuits have 4heretofore been proposed fordiscriminating betweenjspeech and noise byftakingf advantage of therising and falling vocal intervals of speech and utilizing this '-15characteristic to discriminate from more or less continuous noiseenergy. The present invention is in thegnature orfjan improvementA uponvoice operated circuits of* this type.

According to the embodiment of the invention to be describedmorefullyhereinafter, a pair of polarized lrelaysjare.connected inreverse order to theoutput of a low pass filter which in turn fis intheroutput of thedetector circuit to which the sp'eec'hfand'incidentally also the noise '25 currents, areapplied. One of these twolrelays operates immediately @upon the initialv application of speechcurrent to the 'circuit and theother one of these relays` likewiseoperatesimmediately uponfthe cessation of the 'speech Waves.l Noise 0currents which do not have a syllabic characteristie resembling speechare ineffective topper- 'ate either of these two relays. A third relayis preferably provided i in the detector-output cir-f cuit independentof f the lowpass iilter and this 35 relay is arranged to be operated bysteady currents of greater amplitude than the noise thatis incident uponthe system. This relay, for exam-` p1e,`wouldbeY operated by prolongedspeech wave trains and bridge over the'timeinterval between 0 theoperations of the othertworelays. Y `'I'he circuits to be controlledbythe speech'are opere atedwhen any one of'these three relays operatesto shift its armature.` y

The nature and objects of the n be more clearly unders'toodviromk thefollowing detailed Adescription in connection with .theaccompanying'.drawing, the :single iigure of 'whichdiscloses the inventionk suppressorcircuit; i v vThe sing""'gsuppres'sor circuit is illustrated asincorporated in afour-wire circuit .comprising the east vbranch Landthewest branch 2L These branches' are Qppositely Vdirected vone-waycir-` cuits,l assumed tofextend toward'the leftjevenas embodied in a.singing f tually toa subscribers sety through`V the medium,

` invention willk N. Y., a corporationof 1931; serial No. 578,350

(c1. 17a-44) v i oi any suitable transmission system'andtoward theright` to `a, two-way radio or wire transmissionchannel. For; example,the east line may extend to the radio transmitter and the west line tothe radio receiver, or both lines may extend to, a long distanceVtelephone terminalfsuch as an ocean cable'jtelephone terminal.

Line 1 is normally disabled due toa short circuit beinggplaced across'it bythe armature `et relaylO. Line 2 is adapted to be disabled-uponenergization of relay 12vthe armature of which places ak short` circuit`across this line, but relay 12 is normally deenerrgized` so' that jline2 is in condition toj transmit speech. It will'be underlV stoodthattheuse of a short-circuit connection for disabling theline is merelytypical of any rform of disabling that may be. desirable or expedient.vY l f 4It'is theiunction oi the singingvsuppressor to clearthe'eastAline in response tol speech come ing over` this `line from the distant.subscribers station at the `leit and also to disable linev 2., Thespeech" is thuspermittedtobe transmitted over the east circuit, butcurrentssuch vas speech", noise, echoes o r other'disturbances'- kareprevented fromfbeing transmitted over the west circuit. It will lbeunderstood that both circuits 1 and "2 contain one-Way amplifiers'toprovide the neceso.

ysary amplification. n Y .Y

The'singing suppressor is connected to; derive some of Yt'hespeechVwavesffrom line -1 through the hybrid coil yshown at3, this type vofconnection being -used toprevent reilection intoY line 1 of 1` anyimpedances utilized sor branch.' t

v The .voice `wavesderive'd fromfthefline 1; after suitableampliiicationare rdetected by .the duplex detectorshown atA 41;: The`spacepath of `this detector includes :appolar .frelayj15v between thedetectoranode and theyplate *battery as shown; Invthis'same connectionthere is the primary of a in theY singingfsupprestransformer 6thesecondary of` which is con- Y' tionofV whichwill be made clearpresently, Con

denser i4 is connected in anormal series Ycircuit Vfrom battery 15through resistance 16,` condenser 14 and the operate windings ofrelays,10, 1 1 and 12. Upon the operation of any one of the three relays 5,8`or 9, this vcondenser 14 is arranged to be shunted through lresistance17 and inductance 18 .and when so shunted it is discharged at a ratedetermined bythe proportioning of the resistance 17 with respect to thecapacity of 'oo ndenser 14.

The' operation will now `be described. Speech Waves incoming over theline 1 `find this line blocked due to the normal short circuit at theback contact ofrelay 10. A portion of the wavesv passes into the branchcontaining detector 4 by which they arerectied. I 4

These speech waves are not a long continuous wave train, but occur asshort trains of waves of syllable duration. The syllables or vocalintervals occur atthe rate of about 2 to 20 cycles per second. It isfound when speech waves are rectilied, as by the rectifier 4, and arepassed on through a transformer such as 6 and aloWr pass filter such as7, that they produce in the output ofthe filter a current impulse of onesign at, the beginningof a syllable'andanother current impulse ofopposite polarity vat the end of a syllable.

Polar relay 8 is arrangedto attract its armature uponthe initial impulseof a syllable while polar Yrelay 9 attracts its armature on the finalimpulse of a syllable. Y A succession of short syllables therefore, hasthe effect of keeping the armatures of relays 8'and 9 in a stateofyibration.

' In the case of a long sustained speech sound or of a tone which may beapplied to the systemV vfor testing or other purposes, relays S and 9would not be caused to vibrate continuously..

Relay 8 -would roperate upon the beginning of such a long wave train,but would then release itsarmature and relay 9 would not operate untilthe end of such wave train. vThe function of ."relay 5 is to operate incase f la long wave train of. Vsufficient amplitude and thus tofbridgeover the interval between lthe operation of relays 8 and '9. For thispurpose relay'5 can `be made sluggish in its action and is also marginalin ordernot to be operated byA the relatively weak v continuous noisewhich may be present on the system. l l Detector 4 is of the type invwhich, the space current is decreased below normal value when waves areincident upon its input circuit. Re-

lay 5 is shown with its armature normally atpressedonthe detector 4 andpersist for a sufIi-v l tracted. When sufficiently strong waves areimciently longtime, relay 5 releases due to the decrease in the spacecurrent. :I y y When relay 8 operates-to shift its armature Y Y from thenormal position shownvin the drawing to the oppositecontact, all threerelays 10,V 11

and 12 are immediatelyl` energized.` 'Ihis takes place in the followingmanner: As soonas the armature of relay 8 leaves its normal contact, arush of current is allowed to flow through; the

-.condenser 14 frombattery `15 and through the .Irion windings of relays10, 1,1 and 12 in series. "Ihis charging impulse of the condenser 14causes these v relays to operate quickly. When vthe armature of tactsof.relays 9 and 5. V

relays 9 and 5, inductance 18, resistance 16 and battery 15. v` f .Whenat the end ofva syllable relay 9. attracts its armature, the dischargevcircuit of condenser 14 is broken and a rush of charging current flowsinto the condenser and through .the windings of relayslO, 11 and u 12maintaining these` relays operated. When ythe armature of relay 9completes its stroke, a direct current circuit isv closed similar tothat previously traced for relays 10, 11 and 12 but this time includingfront con- By the operation of lrelays 8 and 9 as described, relays 10,11, and` 12 are maintained operated as long as speech .currents arecoming inover line 1. Condenser 14in the manner that khas been describedbridges over the intermittent action of these'relays to maintain apractically steady energizing current in the windings of relays 10, 11and 12.

In the4 case of sustained tonesjory extralcng syllables. relay 5releases its armature, as previouslydescribed, vand maintains thecircuits for relays 10,Y l1 and 12 through its armature and backcontact. Y i Y I At Vthe end of a conversation or during a sufii'-vciently longpau-se, relays ,5, 8 and 9 remain in the condition shown inthe drawing and relays 10 11 and'12 releaseafter a sufiicienthang-over.y

The release of all three relays 5, 8 and 9,*breaks the discharge circuitof condenser 14 (prior to the release of relay 11) and this condenser isallowedY relays are such that relay 11 releases first.y `When Y relay 11.releases it closes at"itsback contact a. ground connection to thelowerterminal of condenser 14 by way of fthe normal contacts f relays 5,8, and 9 and inductance 18."y This 'causes condensery 14 to dischargevthrough the windings of relays 10, 11 and 12 in adirection to releaserelays 10 and 12 simultaneously.v Relay 11 inthis way controlsthe`hang'over timeofrelays y10 and l2. The individualbiasing currents.for these relays are controlled by the associated batteries andvariable Yre'sistances shown. Preferably relaysV 10 and 12 arebiased'alikefrom the same sourceso as to release simultaneously or sothat rel'ay'lO releases slightly ahead of relay 12 to insure'that nosinging circuit is established. For simplicity -the'speech'toiproceedwhile-relay 12 closes the shunt across the opposite branch. Both. ofthese rau conditions are .maintained as long as speech persists. "At thecessation of thespeech these relays arereleasedV after a suitablehang-over time toallow for all of the speech to vpass 'on to circuit 1and to prevent in'circuit 2 echoes 'or otherY disturbances immediately"following the cessationof speech in line k1. f

When speech comes in on circuit 2 a portion of "the speech passesthrough the amplier-detetor A20and operates relay 21 shiftingitsfarrnature froml its back to its'frontrc'ontact. The breaking ofthecircuit at theback Ycontact `o'pen`sf `theV input vcircuit of lowpass filter 7 thus preventing the and 12 from operating even thoughrelay 5 should operate.

What is claimed is:

1. In a voice operatedl circuit a detector on which voice wavesare'impressed, a low-,pass lter in the output of said detector, a pairof polarized n relays having their operating windings connected to theoutput of said lter in respectively reverse direction whereby one or theother of said relays operates at the beginning and at the end of speechimpulses of syllable frequency, and a switching circuit controlledjointly from said relays.

2. A voice operated circuit comprising a detector on which said voicewaves are impressed, a transformer in the output of said detector, alow- I pass lter connected to the secondary of said transformer, saidlter having a cut-off frequency of the order of the syllable frequencyof normal speech, and a pair of polarized relays having their operatingwindings connected to the output of said filter in respectively reversedirection, oney HAROLD J. FISHER.

